Using Diamonds to Create Unhackable Code

IAmTheDave writes "Researchers at Melbourne University have grown diamond particles 1/1000 of a millimetre on optical fibres which they can use to transmit single photons of light at a time. The diamonds are grown on the optical fiber by raining carbon molecules onto the tip of the fiber. They claim that by transmitting information in single photons, any interception of transmitted photons will be useless to the interceptor, and thus the message will be completely unhackable. Transmission speeds are currently slow - 120km/h, but are expected to speed up."

Comments

That's unhackable TRANSMISSIONS, not code

[Chas]

Jeeze.

Re:That's unhackable TRANSMISSIONS, not code

[znu]

The headline probably means code defined as "a system of signals, such as sounds, light flashes, or flags, used to send messages." Rather than computer code.

Re:That's unhackable TRANSMISSIONS, not code

[stonecypher]

You know, by code he means "an encoding," not "a programming language snippet."

"Unhackable Code"?

[cbrocious]

This is far from an "unhackable code". In fact, it's not even a code. Please stop thinking that "quantum cryptography" is a form of cryptography. It's simply an interception-resistant media.

Re:"Unhackable Code"?

[hotspotbloc]

Exactly. When it's too tough to crack the technology then it's time to use social engineering or a key capture hardware device built into a keyboard.

There is nothing unhackable.

Re:"Unhackable Code"?

[cbrocious]

Speaking from the standpoint of someone who does a lot of reverse-engineering (PyMusique/pyTunes was my baby) I'd say that 99% of the time, neither of those methods are neccesary. Usually you can get what you need from either the source or destination directly. Most people seem to overestimate security in computer systems. I just can't wait for "quantum cryptography" to be used for DRM keys so we can have a bit of fun ;)

Re:"Unhackable Code"?

[Kainaw]

Please stop thinking that "quantum cryptography" is a form of cryptography.

That depends completely on how it is used. If I simply send a message in 1s and 0s over the photon stream, it isn't encrypted. I can only be certain that it either got there or it didn't get there.

Cryptography comes in when you encode a message using a photon stream. The mechanics of doing this are old hat by now. It is done in the following steps:

1. Send a stream of, say, 2,000 random 1s and 0s to the other end.
   
2. The other end pics, at random, 500 of the 1s and 0s and sends a plain message back saying only which are chosen - the index, not the value. So, you can both form a 500 bit key (the number of bits is to your choosing)
   
3. Encrypt the message using the key you just worked up and send it.
   

This is commonly said to be 'mostly secure' because it is vulnerable to a man-in-the-middle attack. However, it is tamper-proof once it begins. If anyone attempts to read any of the photons as they travel down the stream, they alter the photons. So, you get a scrambled message at the other end and the hack is immediately known.

Because it cannot be copied enroute without giving away that it is being copied, it is commonly called unhackable. You cannot make a copy of it and send it along while you try and hack it. I know, you are thinking you can just copy the photons and resend new ones with the same message. Nope - you have to know the spin orientation of the photons BEFORE you can read them for a 1 or a 0. If you read it with the wrong spin orientation, you will force it to the orientation you read it as and get an errant 1 or 0 that you incorrectly send down the line. So, you could say it is doubly-encrypted and doubly-protected from in-line hacking.

Re:"Unhackable Code"?

[Anonymous Coward]

Quantum cryptography can't be used for DRM. It's a technique that gives both parties the same random string of bits and this string of bits can be used as a one time pad for transmitting messages across an insecure classical channel.

Re:"Unhackable Code"?

[Kainaw]

Sorry, but, uh, what's step 1?

1. Make a photon stream connection to the other user.

I'm beginning to feel that those typing tapes I bought on late night television aren't working as well as the busom blonde and the short guy with the toupe promised they would.

Re:"Unhackable Code"?

[eddeye]

Quantum Cryptography is indeed real cryptography. It uses the encryption system known as the One Time Pad.

Not long ago, I took a graduate course in quantum computing from a researcher in the field. I wrote a paper for that class specifically on quantum cryptography. In 2001, I worked in the same lab as a physicist building a quantum cryptography device (we had lunch almost every day). I've also studied quite a bit of conventional cryptography. Trust me when I say this:

Quantum cryptography has nothing to do with encryption, and barely anything to do with cryptography. It's an authentic channel with eavesdropping detection (but not prevention). In other words, QC is just a bootstrapping phase to distribute key material (random data) to two parties. Everything you do from that point forward, including everything involving your actual data, is classical crypto on classical channels.

QC has nothing to do with one-time pads. You could use the key material for OTPs, if you're deranged. More likely you'll use something like CBC-AES, CTR-AES, CBC-3DES for encryption, which are much faster (less key material, not limited by QC data rate), simpler, and safer (unless you have the resources of a major world government to oversee proper handling of the data and key material at every point from creation to destruction). At any rate, you'll still need integrity even with a OTP or your data is worthless. That means SHA1-HMAC, CBC-MAC-AES, etc.

Cryptography proper punts on the key distribution issue as it's not solvable mathematically. It's an administrative not an algorithmic problem, putting it outside the domain of modern cryptography. This applies equally to asymmetric crypto; public key databases and root certificates require proper oversight and maintenance. Hence the one problem QC solves, key distribution, is really external (but related) to the field of cryptography. That's why I say the two are orthogonal.

The funny part is, QC isn't even a good solution to key distribution. Its physical requirements are costly, stringent, and limiting. Unless you're an ultra-cautious damn-the-expense client like the US govt, there are more cost effective ways to exchange keys, and much better ways to improve your data's security. QC is a problem in search of a solution.

Re:"Unhackable Code"?

[Minna Kirai]

The funny part is, QC isn't even a good solution to key distribution.

Furthermore, to use QC for key distribution, you already need to have distributed a shared key beforehand! Search for "secret bit string is agreed to" or "a public, but authenticated, channel" in the QC wikipedia page to see what I mean.

Using QC to make an untamperable communication requires you to already have some other comm channel which is already trusted as untamperable- and if you had that, why not just send the keys on it in the first place? (Possible answer is that you can carry a small key on the first, expensive channel, and then use QC for all your later keys for many years. But it'll be a long long time before QC's cost compares favorably to 5 armed guards escorting a briefcase into a jet plane)

Re:"Unhackable Code"?

[tbo]

Summary: parent poster is being a twit.

Long version:
First, let's clarify what it means to say that "physics" guarantees that your quantum key distribution (QKD) system is unbreakable. Given a perfect implementation of the QKD protocol, or at least an implementation where the errors are within certain bounds and you haven't done anything stupid like reusing your OTP, you are guaranteed security if quantum mechanics is correct.

What do I mean by correct? I mean that quantum mechanics correctly describes the relevant systems--systems to which it is currently considered applicable.

We have many good reasons to believe quantum mechanics is correct. Its relativistic extension, QED, has given us some of the most accurately-verified theoretical predictions ever. Notable objections to the theory (such as the famous paper by Einstein, Podolsky, and Rosen, or "EPR") have proven false (google the Bell inequality and the Aspect experiment).

More specifically, some of the particular variations in quantum mechanics that one would imagine could be useful for defeating a QKD system, such as nonlinearity, would give rise to highly unphysical effects (superluminal signaling), which we have not observed.

It seems that quantum mechanics is an island in theory space--that is, any perturbation from the accepted theory seems to give something obviously unphysical, or at least something that does not agree with experiment.

In other words, this is as close to proof as it gets in science. Clearly, quantum mechanics isn't the final word on, say, quantum gravity, but we're not going to be throwing out the undergrad quantum mechanics books any time soon.

Yes, it would be nice to have information-theoretic security, but that doesn't seem to be possible for a key distribution protocol. Still, security predicated on the laws of physics is a hell of a lot better than security-based-upon-the-fact-that-we-haven't-heard -of-anyone-breaking-it, which is all RSA and other popular schemes have going for them (RSA isn't even computationally secure).

Re:"Unhackable Code"?

[Tango42]

It's more complicated than that. The act of observing the photon changes it, so you can't always read it accurately. The method of communication involves checking if you read all the bits correctly afterwards and discarding any you didn't - if you've been reading them in the middle they'll think they read it correctly, but will still have the wrong bit so will get nonsense out when they send a message (probably a simple test message that won't tell you anything useful) and they won't send the real message until they've got rid of you.

Re:"Unhackable Code"?

[Anonymous Coward]

There is only one source on the Wikipedia article on Quantum Cryptography. I find it lacking and possibly misleading, but there are many other sources on the web & beyond that you can read to correlate the good information & gain understanding. Search http://arxiv.org/ among others, although note that not all papers here are peer-reviewed, either.

Common mistakes:

1. This is technology intended for you to do banking.

Sorry for frustrating your grandiose self-delusions, but NSA & DARPA (QuIST) aren't funding the hell out of this type of project in the US to improve your personal banking experience. [but maybe that will only add to your delusions]

2. Because it is quantum (oooh!) it is unbreakable.

All encryption is breakable by some method. And all proofs rely upon assumptions, and some proofs rely on unrealistic or unreasonable assumptions. E.g., I could "prove" relativity to be wrong if I choose assumptions that ignore experimental evidence.

One proof (and an overview of other proofs) of the security of quantum key distribution, i.e., what could come out of the Melbourne group's single photon transmitter:

"Quantum key distribution allows two parties, traditionally known as Alice and Bob, to establish a secure random cryptographic key if, firstly, they have access to a quantum communication channel, and secondly, they can exchange classical public messages which can be monitored but not altered by an eavesdropper, Eve."

So there's your fallible assumption, that A & B have one channel that can be monitored but not altered. (In this proof, Eve can monitor and alter the quantum communication channel if there is another un-alterable channel open between A&B.)

Another explanation is given by Myers in section 2.1, entitled "THEORETICAL IMPOSSIBILITIES IN KEY DISTRIBUTION."

3. Perspective

With the oncoming technology of quantum computing (also not for Joe Slashdot), numerically "difficult" public/private-key encryption schemes are going to be easily breakable. Hence the need for a different scheme. This is the US government, et al., trying to protect themselves against each other when the others figure out quantum computing.

Where's the security?

[shanen]

The original fibre taps just spliced into the fibre and repeated the signals. It's only the later technology that could try to interpret the leakage. I don't see how this adds any security, except perhaps insofar as the time to make the more difficult splice will increase the odds of noticing the interruption. "Unhackable"? Nope. The race will never end.

Re:Where's the security?

[MeanMF]

Adding a repeater in the middle would add latency which could be easily detected by either end by running a few simple tests. Since this is a point-to-point technology your transmission speeds should be predictable and constant.

Re:Question

[The Mighty One]

http://en.wikipedia.org/wiki/Quantum_cryptography Quantum cryptography is an approach to securing communications based on certain phenomena of quantum physics. Unlike traditional cryptography, which employs various mathematical techniques to restrict eavesdroppers from learning the contents of encrypted messages, quantum cryptography is focused on the physics of information. The process of sending and storing information is always carried out by physical means, for example photons in optical fibres or electrons in electric current. Eavesdropping can be viewed as measurements on a physical object---in this case the carrier of the information. What the eavesdropper can measure, and how, depends exclusively on the laws of physics. Using quantum phenomena such as quantum superpositions or quantum entanglement one can design and implement a communication system which can always detect eavesdropping. This is because measurements on the quantum carrier of information disturb it and so leave traces.

Re:Transmission speed?

[Anonymous Coward]

The speed of light depends on what material/gas the light is traveling through.

Yes and no.

[rjh]

Yes and no. Quantum key exchange is, as you point out, a key negotiation protocol which relies on the laws of physics to keep the negotiated key safe from eavesdroppers. However, there's absolutely no limit on the size of key you can generate. If you need a million bits of key, then fine: make a million bit key.

Once you have as many bits of key as you have bits of data, you can treat it as a one-time pad. And that would be a perfectly secure transmission, as long as both sides make sure they destroy the key once it's been used to do an encryption or decryption operation.

In other words, QKE leads quite directly to (a) a cipher and (b) a traditional cryptographic system.

IAAGSSTS (I Am A Grad Student Studying This Shit).

Cryptographically Worthless

[Anonymous Coward]

This is much more complicated than simply sharing one-time-pads. When any two idiots can burn 8GB of random data onto two DVD's and send secure text messages to each other for the rest of their lives, what the hell use is a complex physically secure network like this one? Anyone with enough money and need to buy one can find cheaper and more reliable means of secure communication.

Re:Slowing down light

[Anonymous Coward]

Actually, c is the speed of light in a vacuum. Light can travel more slowly through water, air , glass, etc. This is what causes refraction. You can also get stuff to travel faster than the speed of light through a substance (but not faster than c, for now). Cerenkov radiation is a side effect of neutrons traveling faster than the speed of light through the reactor coolant, creating the light equivalent of a sonic boom.

Re:You are correct.

[aePrime]

Alas, Ph.D. boy, you need to either spend more time studying your courses, or spend more time on your critical reading skills; at this point it's difficult to tell which.

The encryption can be broken, sure, if you know the message. The real beauty in quantum cryptography lies in the fact that intercepting the message (a man in the middle attack) is impossible due to Heisenberg's uncertainty principle.

The January 2005 Scientific American has a good article on it (the cover story, actually).

The next time you're planning on acting so pompous, you may want to check your facts first.

Re:"Unhackable Code"? - 2 things

[Minna Kirai]

AC: In quantum cryptography (which isn't quite what this article is about), there aren't any data lines to monitor -- the information is transmitted by entanglement.

No, your definitions are off. "Quantum Cryptography" is the use of Heisenberg's Uncertainty principle's guarantee that the whole state of a particle cannot be measured to ensure that a message cannot be intercepted and retransmitted.

The use of quantum entanglement to communicate data has also been proposed, but this is known as Quantum Teleportation. QT, not QC.

Re:You are correct.

[m50d]

We have had one time pad ciphers for what, 70 years? When was the last time one was cracked? When some dolt in the kremlin decided to re-use their one time pads. Other than that, it has never been broken. Quantum encryption can be exactly the same - when done right it's unbreakable. Doing it right it hard, but far from impossible

Good challenger for most misleadinfg SD article.

[Ancient_Hacker]

• A quantum channel is only good for as far as one photon is likely to survive above the noise level-- maybe a kilometer at most?
• Anything farther than that will involve detecting the photon and relaying it-- a chancy proposition which adds waay too much noise and of course one can intercept the signal at the repeater.
• Exactly how long can you make a diamond cable? Splices are very unreliable and lossy.
• What is that 120 km number doing in there? Mighty unlikely.

generating SINGLE photons is point of this paper.

[justthisdude]

I think we have wandered a bit from the original article.

All arguments about the workings of quantum encryption can refer to this paper. One key assumption is that you only send a single photon, not two or none. If none arives you wasted that bit-slot, but a second photon allows eavesdropping. Traditional sources generate photons according to Poisson statistics, which means that you can't accurately meter out one photon at a time. The standard fix for this is to attenuate the signal so that the average N is much less than 1 photons per measurement slot. This effectively means you only get (roughly) a photon every 1/N slots, but you still get 2 arriving together every 1/N^2 slot. The first part is both wastful, the second vulnerable.

The current paper merely how to generate single photons more reliably using diamonds as microcavities. Essentially the diamond is a tiny laser resonator on the scale of a single wavelength (1 micron), and can only support one optical mode, so any single spontaneously generated photon goes into that mode, and your output is single, narrow wavelength photon, but no doubles. In some ways this has ceased to be a "L.A.S.E.R." since the Light is not Amplified, and the Emmision of Radiation is not Stimulated, but spontaneous. Maybe I would call it Light Organized from Spontaneous Emission of Radiation, but I digress...

If you wat to look at such microcavities, see this paper

Re:No approximation...

[Sweetshark]

Listen, if the intended receiver is able to pick up the signal, then a man in the middle can, too!
No. Because there is no "the signal". With QC you have two signals on the fiber and you can pick up only one, thereby destoying the other.
I'm not talking about observing the bits that go down the line. I'm talking about impersonating both sides to each other. That is a man in the middle.
Yes. And that wont work.
The other way to make MitM harder is to have a big enough shared secret. You could have secret passwords, or even a secret protocol would work too. If the MitM can't guess the shared secret, then impersonation will fail.
Thats what QC is for. You can generate shared secrets of any size by QC. And the MitM wont be able to guess them, if they are large enough.
Some people have proposed a way of quantum key generation via entangled particles. But remember that getting this shared secret to each other is also subject to MitM attacks.
No! Thats exactly the point! You cant MitM a big QC transmission without notifing the sender/reciever. All the MitM can do is a DoS.
Someone can yoink those entangled particles, and throw in new ones.
Ehem - no. There are *two* things the MitM has to measure because he doesnt know which of those the sender knows about the particle. Though luck for him - his first measurement destroys the particle.
The person you're talking to can always be an impersonator. It can be really improbable, but there is always some possibility. I'm not saying you should be paranoid, but just that every communication involves a degree of trust. Quantum magic won't make that required trust go away.
This is wrong. QC is save from MitM when used with two channels - one QC channel and a public one where transmissions cant be blocked unnoticed (for example radio).
The wikipedia isnt too bad at all about this stuff: http://en.wikipedia.org/wiki/Quantum_cryptography